A tissue elasticity measurement method and device based on wavelength scanning

Abstract

A wavelength-scanning tissue elasticity measurement method and device is described. The invention consists of an excitation module and an imaging module. The excitation module applies force to human tissue, causing tissue indentation and, subsequently, propagation of elastic waves on the tissue surface. The imaging module, based on swept-source optical coherence tomography (OCT), incorporates an optical dispersion component (grating or prism) and utilizes the rapid wavelength scanning capability of the swept-source to convert traditional OCT point scanning into ultra-fast line scanning detection, enabling dynamic tracking and recording of elastic waves in tissue. Finally, the Young's modulus of the tissue is calculated by measuring the elastic wave propagation velocity. Compared to the traditional OCT measurement mode of repeated excitation and repeated imaging at each site, this method's technical breakthrough lies in its ability to complete a measurement in approximately 5ms with a single excitation. This reduces the discomfort associated with repeated excitation and long measurement times during in-vivo measurements of ocular tissue, and avoids adverse factors such as eye closure or eye movement.

Description

Technical Field

[0001] The present invention relates to the technical field related to OCT, and in particular to a tissue elasticity measurement method and a measurement device based on wavelength scanning. Background Art

[0002] Clinical significance of measuring Young's modulus of human tissue

[0003] Tissue Young's modulus is a key indicator for evaluating biomechanical properties, and plays an important role in histological research and clinical practice. In terms of disease diagnosis, by detecting the differences in the Young's modulus of different tissues, it can assist in identifying tumors and assessing the degree of cardiovascular disease and liver fibrosis. During treatment monitoring, based on the changes in Young's modulus during the treatment process, the treatment effects of tumors, cardiovascular diseases, etc. can be judged and treatment strategies can be adjusted. At the surgical guidance level, it provides a mechanical basis for organ transplant suitability assessment and minimally invasive surgical operations, reducing surgical risks. In terms of prognosis, the risk of disease recurrence can be assessed through its recovery status, the degree of patient recovery can be predicted, and clinical precision medicine can be assisted. It can be seen that the measurement of tissue Young's modulus is of great significance in the management of the entire course of the disease.

[0004] The main methods for measuring tissue Young's modulus in clinical practice

[0005] Ultrasound elastography uses a probe to emit ultrasound waves, causing tiny vibrations in tissue. The ultrasound signals reflected back from the tissue are then analyzed to determine how the tissue deforms under elastic forces, thereby calculating the tissue's elastic modulus, also known as Young's modulus. This method allows for real-time, noninvasive imaging of tissues and is used, for example, in examinations of organs such as the breast and thyroid gland to assist in determining whether a tumor is benign or malignant.

[0006] Acoustic Radiation Force Impulse Imaging (ARFI) uses an ultrasound probe to emit high-intensity acoustic pulses into tissue, causing localized, instantaneous displacement. Ultrasound imaging then measures this displacement, allowing the calculation of tissue elastic parameters, including Young's modulus. This technique can be used to measure the elasticity of solid organs such as the liver and pancreas, helping to assess conditions such as liver fibrosis.

[0007] Magnetic resonance elastography (MRE) applies additional low-frequency mechanical vibration to conventional MRI, causing periodic elastic deformation of tissue. The technique then uses an MRI sequence to capture tissue displacement information and uses image analysis techniques to reconstruct the tissue's elastic modulus map, yielding the Young's modulus value. MRE has high resolution for soft tissue and can be used to examine various organs, including the brain, liver, and kidneys. It plays a crucial role in the diagnosis and assessment of brain and liver diseases.

[0008] Atomic force microscopy (AFM) utilizes a highly force-sensitive microcantilever, fixed at one end and equipped with a tiny needle tip at the other. When the needle tip gently contacts the surface of the tissue being measured, the interaction between atoms causes the microcantilever to bend or deflect. The force is measured by detecting the deformation of the microcantilever, and the tissue's Young's modulus is then calculated based on a mechanical model. AFM can manipulate and measure biological samples at the nanoscale, offering unique advantages for studying the mechanical properties of biomolecules and cell surfaces, as well as the elasticity of biomembranes. This provides a deeper understanding of the functions of biomolecules and the physiological and pathological processes of cells.

[0009] Optical coherence elastography (OCE) technology

[0010] Optical coherence elastography (OCE) is a novel imaging technology developed from optical coherence tomography (OCT). It uses elastic parameters such as Young's modulus, shear modulus, stress, and strain of soft tissue as imaging targets, and assesses the mechanical properties of tissue by measuring the tiny displacements and deformations produced by tissues when subjected to external or internal stimuli. With its advantages such as micron-level resolution, real-time image processing, and non-invasive imaging, OCE technology demonstrates great potential in the field of medical diagnosis. OCE technology has broad application prospects in medical diagnosis. In particular, in the diagnosis of cancer, cardiovascular disease, and ophthalmic diseases, OCE can provide information on the mechanical properties of tissues, helping doctors to more accurately diagnose the condition and formulate treatment plans. Furthermore, OCE technology offers the advantages of being non-invasive and high-resolution, making it suitable for a variety of clinical scenarios.

[0011] Conventional OCE uses a MB scanning mode, which involves repeatedly scanning perpendicular to a specific scan line to construct a two-dimensional grayscale image of the tissue based on the optical coherence signal. Dynamic response characteristics, such as displacement amplitude, are then analyzed along the specific scan line by analyzing the time-varying interference signal. This enables comprehensive detection of tissue elastic properties in both temporal and spatial dimensions. However, the repetitive stimulation caused by this scanning can cause discomfort to the subject. For example, in ophthalmic measurements, it can lead to eye closure and movement-induced measurement inaccuracies. This limitation has hindered the widespread adoption of this technology in medical clinical applications, particularly in ophthalmology. Summary of the Invention

[0012] To address the technical deficiencies in the prior art, the present invention provides a tissue elasticity measurement method and device based on wavelength scanning. This method can use a single excitation to complete a measurement in milliseconds (approximately 5 ms), thereby reducing the discomfort caused by repeated excitation and long measurement times during in-vivo eye tissue measurement, and avoiding adverse factors such as eye closure or eye movement caused by these factors. Furthermore, this method can capture images with high resolution and high sensitivity, and through image analysis, objective parameter indicators related to the evaluation of tissue elasticity can be obtained.

[0013] The technical solution adopted by the present invention is: using a tissue elasticity measurement method based on wavelength scanning, comprising the following steps:

[0014] S1, applying a single instantaneous mechanical excitation to the target tissue through the excitation module to generate elastic waves on the tissue surface;

[0015] S2, using a swept-source OCT system, converts the wavelength of the incident beam into a line scan pattern arranged by wavelength via a dispersion component, and collects the dynamic deformation interference signal of the tissue after excitation in real time;

[0016] S3, the imaging module uses continuous acquisition to record the real-time and dynamic changes of tissue morphology under external stimulation;

[0017] S4. Through image analysis, objective parameter indicators related to evaluating tissue elasticity can be obtained.

[0018] Preferably, the step S4 includes the following steps:

[0019] S41. Calculate the tissue displacement or the corresponding phase change corresponding to each frame of the interference signal by using Fourier transform or other algorithms;

[0020] S42, calculating the propagation velocity of the elastic wave by calculating the time-space distribution signal of the phase or displacement;

[0021] S43. Calculate the elastic modulus of the target tissue according to the relationship model between elastic wave velocity and Young's modulus.

[0022] Preferably, the line scanning mode in step S2 is implemented by a prism, a reflective or transmissive grating, to form a line field scan covering the target area.

[0023] Preferably, the system can further expand the one-dimensional line field scanning into two-dimensional surface field scanning through a one-dimensional scanning galvanometer.

[0024] Preferably, the excitation module is one of an air pulse, a piezoelectric transducer or an ultrasonic generator. The excitation application time and the OCT acquisition start time are precisely aligned through a synchronous controller. After the OCT starts acquisition, the excitation function module emits a single excitation at the edge of the target position. After the excitation ends, the OCT continues to acquire to obtain the tissue structure under tissue compression conditions.

[0025] Preferably, the excitation duration of the excitation module is less than 5ms.

[0026] Preferably, the grating assembly is a reflective grating with a groove density of 1200 lines / mm.

[0027] A measuring device for implementing a tissue elasticity measurement method includes an OCT module and an excitation module. The OCT module includes a light source. Light emitted by the light source enters an imaging probe via an optical coupler. The imaging probe is also provided with a collimator along the optical path. After passing through the collimator, the light is emitted toward a grating and scans a tissue sample in parallel through an objective lens. The measuring device also includes a reflector in a reference optical path. After being reflected by the tissue, the OCT detection light returns along the original optical path and is coupled into the optical coupler, generating interference with the light returned by the reflector in the reference optical path. The interference signal is acquired by a detector.

[0028] Preferably, the excitation module is arranged at the front end of the tissue sample to be tested, and exerts force on the human tissue to cause tissue depression, thereby causing phase changes at various positions of the tissue.

[0029] Preferably, a synchronization control module is also included, which is used to coordinate the timing of the acquisition of the OCT module and the excitation application of the excitation module to ensure that the excitation is triggered after the OCT module starts acquiring, and the OCT module continues to acquire at least until the elastic wave decays.

[0030] The present invention provides an ultra-fast, non-contact, quantitative method for measuring human tissue elasticity. Applications include, but are not limited to, tissue structures such as the human cornea (the cornea is shown in the illustration). This wavelength-scanning tissue elasticity measurement method, based on swept-source optical coherence tomography (OCT), incorporates an optical dispersive element (grating or prism) and leverages the rapid wavelength scanning capability of the swept-source to convert conventional OCT point scanning into ultra-fast line scanning detection. This enables dynamic tracking and recording of elastic waves in tissue, and ultimately, calculates the tissue's Young's modulus by measuring the elastic wave propagation velocity. Compared to conventional OCT measurement methods that rely on repeated excitation and repeated imaging at each site, this method's technological breakthrough lies in its ability to complete a measurement in approximately 5 milliseconds with a single excitation. This reduces the discomfort associated with repeated excitation and long measurement times during in-vivo measurements of ocular tissue, and avoids adverse factors such as eye closure or eye movement. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the measuring device of the present invention.

[0032] Figure 2 Schematic diagram of the data processing flow of the present invention; Interference Signal: interference signal; Complex Signal: complex signal; STFT: short-time Fourier transform; PRCD: phase-resolved color Doppler algorithm; Spatial-Temporal Phase Map: spatiotemporal phase distribution map; Spatial-Temporal Displacement Map: spatiotemporal displacement distribution map; Distance-Time Delay Curve: distance-time delay curve; TOF: time-of-flight algorithm; Linear Fitting: linear fitting.

[0033] Among them, 1-OCT module, 2-excitation module, 3-tested eyeball, 4-light source, 5-detector, 6-optical coupler, 7-reflector, 8-collimator, 9-grating, 10-objective lens, 11-cornea, 12-iris, and 13-lens. DETAILED DESCRIPTION

[0034] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0035] A measuring device for implementing a tissue elasticity measurement method includes an optical coherence tomography (OCT) module 1 and an excitation module 2. The OCT module 1 includes a light source 4. Light emitted by the light source 4 enters an imaging probe via an optical coupler 6. The imaging probe is further provided with a collimator 8 along the optical path. After passing through the collimator 8, the light is directed toward a grating 9, where it is dispersed according to wavelength to produce a diffracted beam. The beam is then scanned parallel to the tissue sample via an objective lens 10. The measuring device also includes a reflector 7 in a reference optical path. After reflection from the tissue, the OCT detection light returns along the original optical path and couples into the optical coupler 6, where it interferes with the light returned by the reflector 7 in the reference optical path. The interference signal is captured by a detector 5. The excitation module 2 is positioned at the front end of the tissue sample to be measured and applies force to the human tissue, causing tissue depression and, subsequently, propagation of elastic waves on the tissue surface. A synchronization control module is also included to coordinate the timing of acquisition by the OCT module 1 and the excitation application by the excitation module 2, ensuring that excitation is triggered after the OCT module 1 begins acquisition and that the OCT module 1 continues acquisition at least until the elastic waves have decayed.

[0036] The excitation module can use a variety of external excitation methods, including but not limited to air, PZT, and ultrasound. The illustration uses an air excitation module. This module's primary function is to apply a specific form of excitation to biological tissue, causing measurable microdeformations. This method allows for the acquisition of information about the elastic properties of tissue under load, as tissues of varying elasticity will deform to varying degrees and patterns under the same excitation. The excitation module provides the foundation for obtaining quantitative parameters of tissue elasticity. By precisely controlling excitation parameters such as intensity and frequency, combined with subsequent optical measurements and data analysis, quantitative indicators such as the tissue's elastic modulus can be calculated, providing more accurate and objective evidence for medical diagnosis and research. The OCT module and the excitation module must operate synchronously. After OCT acquisition begins, the excitation module emits a single excitation at the edge of the target location. After excitation ends, OCT acquisition continues to capture tissue structure under conditions of tissue compression.

[0037] Example 1

[0038] The system uses a swept-source laser with a 100 nm bandwidth and a 100 kHz repetition rate. A reflection grating with a groove density of 1200 lines / mm is incorporated into the sample arm after the collimator. Wavelength scanning is then performed using the first-order diffracted beam from the grating. A 50 mm focal length objective lens creates a line focus on the sample with a length of 6.285 mm and a total power of 1.0 mW.

[0039] After being excited by an air pulse, the system repeatedly acquires 512 a-lines, each containing 1024 points. Scanning the wavelength-dispersed beam in the spatial dimension yields a two-dimensional dataset of 1024 × 512 points. At a line scan rate of 100 kHz, a single measurement can be completed in approximately 5 ms.

[0040] Data processing includes the following steps:

[0041] (1) Set a sliding window with a width of 64 pixels and a step size of 5 pixels, and use the sliding window to perform short-time Fourier transform on the interference signal. Therefore, each a-line data has 193 segments, each containing 32 complex signals;

[0042] (2) Considering all segments at the same position in the time dimension, a subset of 32 × 512 points is formed. The phase difference Δϕ between the a-lines separated by 5 pixels at each position is calculated using the phase-resolved color Doppler (PRCD) algorithm;

[0043] (3) After all subsets are processed, the three-dimensional data sets of each phase are projected axially onto the spatiotemporal phase distribution map. Finally, a further displacement map is obtained;

[0044] (4) The time-of-flight method is used to calculate the displacement delay of each segment. The group velocity can be determined by linearly fitting this distance-time delay curve.

[0045] The results are as follows Figure 2 shown.

[0046] It should be noted that although the present invention has been described in the above specific embodiments, the inventive concept of the present invention is not limited thereto. Any improvements or variations based on the inventive concept are protected by this patent.

[0047] The above is only a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiments and experimental examples. Any technical solution that follows the concept of the present invention is included in the scope of protection of the present invention. It should be emphasized that for ordinary technicians in this technical field, without departing from the purpose and scope of the present invention, any modification or equivalent replacement should be regarded as part of the scope of protection of the present invention.

Claims

1. A measuring device for measuring tissue elasticity, characterized in that: The measuring device comprises an OCT module (1) and an excitation module (2), wherein the OCT module (1) comprises a light source (4), and the light source is 100 kHz swept frequency source laser, the light emitted by the light source (4) enters the imaging probe through the optical coupler (6), the imaging probe is also provided with a collimator (8) along the optical path direction, the light passes through the collimator (8) and is emitted to the grating (9), and is scanned in parallel by the objective lens (10) to scan the tissue sample, and the dispersion component grating expands the light spot emitted by the broadband swept frequency light source into a one-dimensional line field scan, the measuring device also includes a reflector (7) in the reference optical path, the OCT detection light is reflected by the tissue, returns through the original optical path, and is coupled into the optical coupler (6), and interferes with the light returned by the reflector (7) in the reference optical path, and the interference signal is obtained by the detector (5), and also includes a synchronization control module, the synchronization control module is used to coordinate the timing of the acquisition of the OCT module (1) and the excitation application of the excitation module (2), to ensure that the excitation is triggered after the OCT module (1) starts to acquire, and the OCT module (1) continues to acquire at least until the elastic wave attenuation ends, and the excitation module applies a single excitation.

2. The measuring device according to claim 1, characterized in that The excitation module (2) is arranged at the front end of the tissue sample to be tested, and exerts force on the human tissue, causing the tissue to collapse, thereby causing the propagation of elastic waves on the tissue surface.

3. A method for measuring tissue elasticity based on wavelength scanning using the measuring device according to claim 1, characterized in that: The following steps are involved: S1. Apply a single instantaneous mechanical excitation to the target tissue through an excitation module to generate elastic waves on the tissue surface. The excitation module is one of an air pulse, a piezoelectric transducer, or an ultrasonic generator. The excitation application time is precisely aligned with the OCT acquisition start time through a synchronization controller. After the OCT starts acquisition, the excitation function module emits a single excitation at the edge of the target position. After the excitation ends, the OCT continues to acquire to obtain the propagation state of the elastic wave on the tissue; S2, using a swept-source OCT system, converts the wavelength of the incident beam into a line scan pattern arranged by wavelength via a dispersion component, and collects the dynamic deformation interference signal of the tissue after excitation in real time; S3, the imaging module uses continuous acquisition to record the real-time and dynamic changes of tissue morphology under external stimulation; S4. Through image analysis, objective parameter indicators related to evaluating tissue elasticity can be obtained.

4. The method for measuring tissue elasticity based on wavelength scanning according to claim 3, characterized in that: The step S4 comprises the following steps: S41. Calculate the tissue displacement or the corresponding phase change corresponding to each frame of the interference signal by using Fourier transform or other algorithms; S42, calculating the propagation velocity of the elastic wave by calculating the time-space distribution signal of the phase or displacement; S43. Calculate the elastic modulus of the target tissue according to the relationship model between elastic wave velocity and Young's modulus.

5. The method for measuring tissue elasticity based on wavelength scanning according to claim 3, characterized in that: The line scanning mode in step S2 is realized by a prism, a reflective or transmissive grating, forming a line field scan covering the target area, and the one-dimensional line field scan is expanded into a two-dimensional surface field scan by a one-dimensional scanning galvanometer.

6. The method for measuring tissue elasticity based on wavelength scanning according to claim 3, characterized in that: The excitation duration of the excitation module is less than 2ms.

7. The method for measuring tissue elasticity based on wavelength scanning according to claim 3, characterized in that: The dispersion component is a grating.

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